1. Technical Field
The present disclosure relates to a vehicle headlamp. More particularly, the present disclosure relates to a vehicle headlamp that can secure good conductivity between a reflector and a socket and can reduce the size of a vehicle headlamp by forming a conducting portion, which is connected to a conductive member to transmit noise generated when the discharge lamp is turned on, on a certain surface of a case of the socket.
2. Related Art
For example, there is a vehicle headlamp where a lamp unit, which includes a light source and a reflector reflecting light emitted from the light source, is disposed in a lamp outer case, which includes a cover and a lamp housing.
There are vehicle headlamps where a discharge lamp is used as the light source and a lighting device supplies drive current to the discharge lamp in order to turn on the discharge lamp (see e.g., JP-A-2007-317453 and JP-A-2005-302743).
The lighting device may include an electric power supply, a control unit, a high-voltage generator, and the like. The electric power supply may include a lighting circuit unit, for example, a switching element, and supplies electric power to the discharge lamp. The control unit controls the electric power supplied to the discharge lamp. The high-voltage generator includes a starting circuit referred to as a starter that turns on the discharge lamp by generating a high voltage in the discharge lamp.
In the vehicle headlamp described in JP-A-2007-317453, the lighting device includes: a socket that includes a case for holding a predetermined structure and a connection portion connected to a cap of the discharge lamp; a device body that is disposed at a lower end portion of a lamp outer case; and a connecting cable that is connected to the device body and the socket. The electric power supply, the control unit, the high-voltage generator, and the like are disposed in the device body.
In the vehicle headlamp described in JP-A-2005-302743, the lighting device includes: a socket that is connected to a cap of the discharge lamp; a device body that is disposed at a lower end portion of a lamp outer case; and a connecting cable that connects the socket to the device body. The electric power supply and the control unit are disposed in the device body, and the high-voltage generator is disposed in the socket.
In the vehicle headlamp using a discharge lamp as the light source, there is a concern that noise is generated when the discharge lamp is turned on, which has a negative influence on devices in the vehicle, for example, a communication device such as a radio. For this reason, the noise needs to be transmitted along a predetermined path and be grounded.
Accordingly, in the above-mentioned vehicle headlamps, a conductive member, such as a leaf spring member, is mounted at the rear end portion of the reflector having conductivity, an outer peripheral surface of the case forms the socket so as to have conductivity, and the conductive member and the outer peripheral surface of the case are connected to each other and grounded, while the connection portion of the socket is connected to a cap of the discharge lamp, thereby preventing an bad influence caused by the generation of noise.
Meanwhile, in the structure where the conductive member and the outer peripheral surface of the case of the socket are connected to each other for grounding as described above, the conductive member is positioned at the periphery of the case. Accordingly, the vehicle headlamp increases in size toward the periphery of the case, and thus size reduction of the vehicle headlamp is hindered.
In the vehicle headlamp described in JP-A-2005-302743, the high-voltage generator is disposed in the socket, and thus the socket in particular increases in size toward the periphery of the case. For this reason, it is difficult to reduce the size of the vehicle headlamp.